Vented filter cartridge for water treatment device

ABSTRACT

A filter cartridge has a shell defining an upper portion with an upper interior volume and a lower portion with a lower interior volume. The cartridge is for use in gravity-fed water treatment systems have an upper untreated supply and a lower filtered container. A hydrophilic porous particulate carbon powder block filter in a polymeric binder is disposed in the cartridge. The filter has a central opening and is open on both ends. The top end of the block is fitted with an air vent tube. The lower end of the block is fitted into a rubber gasket to direct water flow into the lower container. As water flow through the filter cartridge, air is vented through the block filter central opening and out through the vent tube.

BACKGROUND OF THE INVENTION

This invention relates to a replaceable filter cartridge for use in agravity-fed water treatment system. In particular this invention relatesto a novel structural filter cartridge for a carafe/pitcher system in anair vent facilitates water flow and in which only the carbon block isreplaceable.

Carafe/pitcher water filtration systems are batch treatment andfiltration devices in which water is filtered, treated and stored in acontainer. The treated water is discharged from a spigot on thecontainer, providing a self-contained water treatment system. Theseself-contained systems typically have upper and lower chambers separatedby a filter cartridge.

The water treatment process relies on gravity to force water through thefilter cartridge to remove harmful contaminants from the water. Theupper chamber receives untreated water to be filtered while the lowerchamber receives and stores the filtered water. The water is forcedthrough the filter cartridge by gravity.

The presence of unwanted and potentially harmful contaminants indrinking water are a cause for health concern. As such, there is adesire for water treatment devices suitable for use in the home and asportable instruments for water treatment. As a result, many watertreatment devices and methods have been developed to remove contaminantsor otherwise treat the water to obtain a suitable drinking water.

Some of these water treatment devices and methods utilize treatmentmaterials, which, of their own nature, can be distasteful to consumersof the treated water. For example, municipal water treatment facilitiesuse chlorine as an active agent to remove bacterial contaminants but theodor and taste of the treated water can be offensive. It is known to useactivated carbon to treat water to remove the offensive odor and tasteof chlorine-treated water, however, the flow rate of water through theactivated carbon can be hampered. When the life of the carbon has beenexhausted, the entire cartridge, that is the plastic housing containingthe carbon is discarded along with the carbon.

In addition to chemical and particulate contaminants, several types ofharmful contaminants in drinking water are a cause for health concern.Even municipal water treatment fails to adequately remove all of thehazardous contaminants. Most municipal systems use chlorine asdisinfectant to remove bacteria. It is known that excess chlorinenormally used by the municipality is in itself a source to createharmful chemicals commonly known as disinfectant by products, (DBP).These DBP, along with herbicides and pesticides, often present and knownas volatile organic chemicals (VOCs), are harmful chemicals in the watersystem. Besides these volatile organic chemical contaminants, biologicalcontaminants including protozoan cysts as Giardia lamblia andCryptosporidium, excreted by animals, are present in certain waters.

Cysts are not easily removed by conventional oxidizing agents. Commonmethods of removing cysts are to trap them in a filter that has aporosity less than 2 microns. Such filters with pore sizes less than 2microns typically are used in water purification systems that use highwater line pressure.

Gravity filtration is one of the oldest ways of filtering water.Starting from a simple filter cloth to remove suspended impurities tocarbon granules along with certain ion exchange media to remove chlorineand certain heavy metals, gravity filtration systems have upper andlower chambers separated by filter cartridge. The system relies ongravitational forces acting on the untreated water in the upper chamberto force the water through the cartridge and into the lower chamber toproduce filtered water.

Gravity filtrations systems in residential use vary in sizes, defined bythe capacity of the two chambers. One such gravity filtration system incommon residential use is the carafe type of filter with the topcontainer having a capacity less than 3 liters. The pressure of theuntreated water is sufficient to force the water through a limitedamount of activated carbon granules and ion exchange resins.

Replaceable filter cartridges for household use are known. In onedevice, a filter cartridge contains particles of activated charcoal andcarbon or other suitable absorbent material. Water is filtered bypassing it through the tubular wall of the cartridge from the spacebetween the cartridge and the housing toward the inside of the tubularcartridge. The filter cartridge is generally cup-shaped and thecartridge structure provides a long flow path for water traveling fromthe inlet to the outlet. This provides effective odor and tastefiltering of the water due to the long contact time.

In another system, a filter tube has a plurality of randomly disposedglass fibers having interstices to define the porosity of the filter.The glass fibers are bonded at the junctions of the fiber cross-overswith a hardened silicone resin bonding agent. However, the bonding agentcan impart hydrophobicity to the filter and restrict the scope of thefilter applications in that organic bonding agents can have a color,which darkens with sunlight and use.

Another system discloses a pass-through pitcher filter that has acompact filter element including a thin annular disk of molded granularactivated carbon and a peripheral annular seal element. The seal elementallows the filter to be replaceably mounted on the lower end of an upperplastic reservoir, and the reservoir is adapted to be supported in thetop of a pitcher for receiving filtered water. The plastic reservoir andfilter are placed on a pitcher for receiving and dispensing the treatedwater. This assembly relies on gravity flow of water from the reservoirto the pitcher via the filter. The seal element utilizes a syntheticrubber material and is preferably molded around the carbon filter disk.

The filter element is made from a rigid sintered block of activatedgranular carbon and includes a suitable binder, such as polyethylene,compressed and heated to form a molded porous block. An annularsynthetic rubber seal is attached to the periphery of the carbon block.However, when the filter element is used initially or after it hasremained unused for a period of time, surface tension between water inthe reservoir which is to be filtered and the dry porous carbon blockmay inhibit normal gravity flow of the water through the filter element.To initiate flow, manual pressure is applied to a bellows element of thereservoir to compress air in the reservoir to force water through thecarbon block to initiate water flow.

Yet another system includes a filter cartridge for a gravity-fed watertreatment device that has a hydrophilic porous particulate filter withan interior volume filled with granular filter activated carbon, an ionexchange resin or a combination of granular carbon and resin. The porousparticulate filter is microporous and has a pleated sheet filter media,and is arranged to establish with a pressure of about 0.5 pounds persquare inch (psi) a flow rate of water by gravity through the filtercartridge.

Such a device has a low flow rate, which is not practical for a gravityfed water treatment device. To overcome the low flow rate, the porousparticulate filter contains a hydrophilic material. Moreover, such adevice does not typically remove volatile organic chemicals, and it isnot capable of doing so without specified treating chemicals ormaterials.

Accordingly, there is a need for a water filter having improved fluidflow over known filters. Desirably such a filter has a removable filtermedium adapted for field removal, cleaning, and replacement. Moredesirably, such a filter is capable of removing harmful chemicals knownas disinfectant byproducts (DBP) and volatile organic chemicals (VOC)and protozoan cysts, as well as heavy metals such as lead, cadmium andmercury. More desirably still, such a water filtering system uses carbonblock filter that are bio-static such that any trapped bacteria will notmultiply and grow.

BRIEF SUMMARY OF THE INVENTION

A filter cartridge for a gravity-fed water treatment device includes acartridge shell defining an upper portion having an upper interiorvolume and a lower portion having a lower interior volume. The lowerportion has openings therein. The shell includes a top cap havingopenings therein. The top cap is mounted to the lower part of thecartridge shell.

A hydrophilic carbon block having an outer wall and a central openingdefining an inner wall is positioned in the shell. The carbon block hasa block cap disposed on a top of the carbon block. The block cap has acentral opening therein.

A sealing member extends about the cartridge shell lower portion. Thesealing member supports a bottom of the carbon block. The sealing memberhas an opening therein aligning, at least in part, with the carbon blockcentral opening and open to the lower interior volume.

A vent tube extends upwardly through the block cap and the top cap. Thevent tube is sealed at about the block cap opening and has a vent tubeoutlet disposed upwardly a predetermined distance.

The filter cartridge receives a source of untreated water through thetop cap openings and supplies treated water through the cartridge shelllower portion openings. The filter cartridge is disposed between theuntreated water source and the treated water supply. Water flows byforce of gravity through the top cap openings, through the hydrophiliccarbon block from the outer wall to the central opening, and through theshell lower portion openings. Air is vented from the lower portion lowerinterior volume through the vent tube and the vent tube outlet. The ventoutlet is located at a height greater than a maximum height of water inthe filter cartridge.

An O-ring can be disposed between the vent tube and the block cap toprevent untreated water from flowing into the central opening bypassingflowing through the carbon block wall. The vent tube has an open tophaving a cap thereon and the vent tube outlet is one or more openings ina side wall of the vent tube.

In a preferred embodiment, the hydrophilic carbon block is formed as acylinder having an open, longitudinal central region. The carbon blockcan be formed from a polymeric binder and an activated carbon powder.Preferably, the carbon block is surface treated for hydrophilicity. Thepolymeric binder can be, for example, an ultrahigh molecular weightpolyethylene. A preferred binder has a molecular weight of about threemillion molecular weight.

The carbon block can be surface treated with an anionic surfactantwetting agent, such as diethylhexyl sodium sulfosuccinate. A presentblock has a wall thickness measured between the outer wall of about 3 mmto 10 mm. The activated carbon powder has a mesh size of about 40×300and preferably about 40×140.

These and other features and advantages of the present invention will beapparent from the following detailed description, in conjunction withthe appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The benefits and advantages of the present invention will become morereadily apparent to those of ordinary skill in the relevant art afterreviewing the following detailed description and accompanying drawings,wherein:

FIG. 1 is an elevational view, shown in partial section, of a filtercartridge embodying the principles of the present invention;

FIG. 2 is an exploded perspective view of the filter cartridge of FIG.1; and

FIG. 3 is a sectional view of the filter cartridge shown in an exemplarycarafe or pitcher.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describeda presently preferred embodiment with the understanding that the presentdisclosure is to be considered an exemplification of the invention andis not intended to limit the invention to the specific embodimentillustrated.

It should be further understood that the title of this section of thisspecification, namely, “Detailed Description Of The Invention”, relatesto a requirement of the United States Patent Office, and does not imply,nor should be inferred to limit the subject matter disclosed herein.

Most gravity-type filtration systems for typical home use are pourthrough pitcher-type systems. In such a system, activated carbongranules are filled in the bottom of a cartridge to form a carbon“column” to contact the water and remove bad taste and odor. In somefilter systems, ion exchange resin is added to the activated carbon toremove heavy metals.

The carbon granules are usually of mesh size of 20×50 and use about 50grams per cartridge. This has a limited capacity and requires fairlyfrequent replacement in order to remain effective. In replacing thesecartridges, the entire cartridge including any plastic housing or bodyis discarded along with the carbon filter medium.

Carbon blocks made of activated carbon powder can provide enormoussurface area to remove volatile organic chemicals in addition toremoving bad taste and odor. Depending on particle size and sizedistribution of the carbon particles, the block can be of variousnominal porosities. Conventional carbon blocks are generally tubular indesign, and having a central opening or bore. Water flows from the outersurface radially inwardly, through the wall into inner bore of thecarbon block. For water to flow at an acceptable rate through the carbonblock, the water requires a driving force greater than gravity. As such,these system are generally used in homes with a water line connection toprovide the motive force. And, for cysts reduction ability, carbonblocks typically have a porosity of less than 2 microns.

However, in a gravity filter system, particularly the carafe type offilter it is desirable to use carbon blocks instead of carbon granulesto increase the adsorption capacity of the filter. Bommi et al., U.S.Pat. No. 7,396,461, which is commonly assigned with the presentapplication and is incorporated herein by reference, teaches a domeshaped carbon block to increase the surface area coupled with ahydrophilic surface modified binder to increase the flow rate to anacceptable level for gravity application.

Accordingly, referring to the figures, there is shown a filter system 10that uses a carbon block 12 of tubular design positioned in a cartridgehousing 14, embodying the principles of the present invention. Thecarbon block 12 is easily replaceable and discarded, while the plasticcartridge housing 14 is reused. In known commercially availablepitchers, the cartridge including the plastic housing along with thecarbon media is discarded which is not eco-friendly design.

In the present filter system 10, activated carbon powder of mesh size40×300 is used, and preferably carbon powder having a mesh size of40×140 and 140×200 is used in making the carbon block. Activated carboncan be manufactured from various sources, including bituminous, peat andwood. A preferred source for the carbon is coconut shell based activatedcarbon. Coconut shell is preferred because of its wide availability andbecause it is a renewable resource. One known replaceable carbon blockfilter is made from coconut shell based activated carbon, manufacturedby and commercially available from Global Ecocarb Pvt Ltd, of Indiaunder the trademark GREENCARBON®.

In manufacture of the carbon block 12, coconut shells are charred in anenvironmentally friendly process, emitting no methane into theatmosphere. The carbon block 12 can be surface modified to increase itshydrophilicity. One suitable surface treatment is an anionic surfactantwetting agent, such as diethylhexyl sodium sulfosuccinate. The carbonblock 12 can also be surface modified to increase its kinetics to beable to remove heavy metals such as lead, cadmium and mercury. Thecarbon block 12 can also be impregnated with silver to providebio-static characteristics to prevent the growth of bacteria and theconsequent fouling of the carbon.

The carbon block 12 can be formed from a hydrophilic material and caninclude a polymeric binder and the activated carbon powder. A suitablepolymeric binder is an ultrahigh molecular weight polyethylene. Such apolymeric binder has a molecular weight of about three millionmolecular.

FIG. 3 illustrates an assembled cartridge 18 in a pitcher or carafe 16.Water to be filtered UW is poured into the top container 20 of thepitcher 16 and filtered water FW is collected in a bottom storagecontainer 22. The cartridge assembly 18 provides flow communicationbetween the top container 20 and the bottom container 22.

As seen in FIGS. 1 and 2, the cartridge assembly 18 includes a plastichousing 14 having upper and lower portions, 24, 26, respectively, and inwhich the replaceable carbon block filter 12 is housed. The upperportion or cap 24, has openings 28, exemplary of which are the verticalslots, through which water enters the cartridge 18. The lower portion 26is formed as a sealed unit with an opening 30 in the bottom 32. In apresent unit, a collar 34 extends upwardly from the base 32 of the lowerportion 26 to define the opening 30. The carbon block 12 has a bottomcap 36 made of a bio-degradable plastic. The bottom cap 36, which issealed to the bottom of the carbon block 12, is held in place at thebottom 32 of the plastic housing 26, cooperating with the opening 30 inthe bottom of the lower portion 26 by a seal 38, such as the illustratedO-ring. In this arrangement, the interior or bore 40 of the block 12 isin flow communication with the bottom storage region 22 of the pitcher16.

The top of the carbon block filter 12 has an end cap 42 that is alsomade of bio-degradable plastic. The top end cap 42 has an outlet 44 andan air vent tube 46 is held in place in the outlet 44 by a seal 48, suchas the exemplary O-ring. The top end cap 42 is sealed to the carbonblock 12.

The air vent tube 46 is closed at the top 50 and includes a plurality ofholes 52, such as pin holes at an upper end 54 of the vent tube 46. Theperforated tube 46 provides a path for the escape of air that is presentin the bottom container 22 that is displaced by water flowing into thebottom container 22. Without the vent path, the pressure in the bottomcontainer 22 would increase as water enters the bottom container 22,thus providing increased resistance to water flow.

A plastic cover 24, such as the illustrated perforated cover is fittedon to the top of the lower portion 26 of the plastic housing 14. Thecover 24 can be secured in place on the housing by a friction fit, athreaded or bayonet mount, or other removable mounting. In thisarrangement water in the upper compartment 20 of the pitcher 16 isisolated from water in the bottom storage region 22 by the carbon block12.

To increase the flow rate through the block 12 and to optimize thesurface area over which filtration occurs, the height h₁₂ of thereplaceable carbon block 12 is configured to occupy part of the topcontainer 20 and part of the bottom container 22. Also to increase theflow rate it is desirable to have the water flow from the outer surface56 of the block 12 to the inner bore 40.

Water to be filtered UW flows from the top container 20 through theopenings 28 in the cover 24 and flows through the carbon filter 12. Aswater flows into the carbon block 12, air inside the porous block 12 isallowed to escape through the air vent tube 46. It has been found thatthe release of air through the vent tube 46 facilitates an increase inwater flow rate through the carbon block 12. Filtered water FW thenflows from out of the bore 40 (at the bottom of the block) and iscollected in the bottom container 22.

When it is desired to replace the carbon block 12, the air vent tube 46is pulled out from the top of the carbon block 12 and the cover 24 isopened. The replaceable carbon block 12 is simply pulled out of theplastic housing 14 lower section 26. In such a configuration, only thereplaceable carbon block 12 is discarded and the plastic housing lowersection 26, air vent tube 46 and cover 24 are re-used, greatly reducingthe amount of materials that are treated as waste.

It will be appreciated by those skilled in the art that the presentfilet system 10 is not limited to any specific height or diameter orthickness of carbon block 12. Indeed, the dimensions of the block 12will vary, depending upon on the pitcher/carafe 16 configuration andspecifications, such as, the water height in the top container 20 andthe desired flow rate. In a present filter system 10, the block 12 has awall thickness t₁₂ measured between the outer wall 56 and the inner wall58 of about 3 mm to about 10 mm.

In addition, the present vented filter system 10 is not limited to apitcher/carafe 16 application but can be used in any gravity-type systemin which water to be purified flows under gravity pressure from an uppercontainer to a lower container through the filter assembly 10.

Moreover, it will be understood that based on the impurities in thewater, the size and shape of the media holding chamber in the housing 14can be varied to increase contact and dwell time as desired toaccommodate bacteria and virus eradicating media.

All patents referred to herein, are incorporated herein by reference,whether or not specifically done so within the text of this disclosure.

In the present disclosure, the words “a” or “an” are to be taken toinclude both the singular and the plural. Conversely, any reference toplural items shall, where appropriate, include the singular.

From the foregoing it will be observed that numerous modifications andvariations can be effectuated without departing from the true spirit andscope of the novel concepts of the present invention. It is to beunderstood that no limitation with respect to the specific embodimentsillustrated is intended or should be inferred. The disclosure isintended to cover by the appended claims all such modifications as fallwithin the scope of the claims.

1. A filter cartridge for a gravity-fed water treatment devicecomprising: a cartridge shell defining an upper portion having an upperinterior volume and a lower portion having a lower interior volume, thelower portion having openings therein; a top cap having openingstherein, the top cap being mounted to the lower part of the cartridgeshell; a hydrophilic carbon block having an outer wall and a centralopening defining an inner wall, the carbon block having a block capdisposed on a top of the carbon block, the block cap having a centralopening therein; a sealing member extending about the cartridge shelllower portion, the sealing member supporting a bottom of the carbonblock, the sealing member having an opening therein aligning, at leastin part, with the carbon block central opening and open to the lowerinterior volume; and a vent tube extending upwardly through the blockcap and the top cap, the vent tube being sealed at about the block capopening, the vent tube having a vent tube outlet disposed upwardly apredetermined distance, wherein the filter cartridge receives a sourceof untreated water through the top cap openings and supplies treatedwater through the cartridge shell lower portion openings, wherein thefilter cartridge is disposed between the untreated water source and thetreated water supply, the water flowing by force of gravity through thetop cap openings, through the hydrophilic carbon block from the outerwall to the central opening, and through the shell lower portionopenings, and wherein air is vented from the lower portion lowerinterior volume through the vent tube and the vent tube outlet, the ventoutlet being located at a height greater than a maximum height of waterin the filter cartridge.
 2. The filter cartridge in accordance withclaim 1 including a filter sheet disposed in the cartridge shell lowerportion overlying the lower portion openings.
 3. The filter cartridge inaccordance with claim 1 including an O-ring disposed between the venttube and the block cap to prevent untreated water from flowing into thecentral opening bypassing flowing through the carbon block wall.
 4. Thefilter cartridge in accordance with claim 1 wherein the vent tube has anopen top having a cap thereon and wherein the vent tube outlet is anopening in a side wall of the vent tube.
 5. The filter cartridge inaccordance with claim 4 including a plurality of vent tube outlets. 6.The filter cartridge in accordance with claim 1 wherein the hydrophiliccarbon block is formed as a cylinder having an open, longitudinalcentral region.
 7. The filter cartridge in accordance with claim 1wherein the hydrophilic carbon block is formed from a polymeric binderand an activated carbon powder, the carbon block being surface treatedfor hydrophilicity.
 8. The filter cartridge in accordance with claim 7wherein the polymeric binder is an ultrahigh molecular weightpolyethylene.
 9. The filter cartridge in accordance with claim 7 whereinthe surface treatment is with an anionic surfactant wetting agent. 10.The filter cartridge in accordance with claim 9 wherein the anionicsurfactant wetting agent is diethylhexyl sodium sulfosuccinate.
 11. Thefilter cartridge in accordance with claim 7 wherein the molecular weightof the polymeric binder is three million molecular weight.
 12. Thefilter cartridge in accordance with claim 1 wherein the carbon block hasa wall thickness measured between the outer wall and the inner wall andwherein the wall thickness is about 3 mm to 10 mm.
 13. The filtercartridge in accordance with claim 6 wherein the activated carbon powderhas a mesh size of about 40×300.
 14. The filter cartridge in accordancewith claim 6 wherein the activated carbon powder has a mesh size ofabout 40×140.